Shrinkage and Mechanical Properties of Self-Compacting SFRC With Calcium-Sulfoaluminate Expansive Agent.

Changyong Li,Meng Feng,Shunbo Zhao,Pengran Shang,Fenglan Li

doi:10.3390/ma13030588

Abstract

With the premise of ensuring workability on a fresh mixture, the volume stability of hardened self-compacting steel fiber reinforced concrete (SFRC) becomes an issue due to the content of cementitious materials increased with the volume fraction of steel fiber. By using the expansive agent to reduce the shrinkage deformation of self-compacting SFRC, the strength reduction of hardened self-compacting SFRC is another issue. To solve these issues, this paper performed an experimental investigation on the workability, shrinkage, and mechanical properties of self-compacting SFRC compared to the self-compacting concrete (SCC) with or without an expansive agent. The calcium-sulfoaluminate expansive agent with content optimized to be 10% mass of binders and the steel fiber with a varying volume fraction from 0.4% to 1.2% were selected as the main parameters. The mix proportion of self-compacting SFRC with expansive agent was designed by the direct absolute volume method, of which the steel fibers are considered to be the distributed coarse aggregates. Results showed that rational high filling and passing ability of fresh self-compacting SFRC was ensured by increasing the binder to coarse-aggregate ratio and the sand ratio in the mix proportions; the autogenous and drying shrinkages of hardened self-compacting SFRC reduced by 22.2% to 3.2% and by 18.5% to 7.3% compared to those of the SCC without expansive agent at a curing age of 180 d, although the expansion effect of expansive agent decreased with the increasing volume fraction of steel fiber; the mechanical properties, including the compressive strength, the splitting tensile strength, and the modulus of elasticity increased with the incorporation of an expansive agent and steel fibers, which met the design requirements.

Highlights

To overcome the casting difficulty of concrete in structural members and joints with complex shapes and dense reinforcements, and to reduce the environmental pollution of vibration noise, a high-performance self-compacting steel fiber reinforced concrete (SFRC) becomes more and more applicable in engineering structures [1,2,3,4]
With the vf increased from 0.4% to 1.2%, the DJ decreased by 2.9% and the to diameter of 50cm (T50) increased by 16.4%, while the diameter between slump-flow and J-ring flow (D-DJ) increased from 20 mm to 30 mm, indicating that the viscosity increased and the passing ability decreased by the presence of steel fibers; the slump-flow did not vary obviously due to the increase of binder to coarse-aggregate ratio
With the premise of ensured workability of a fresh mixture, this paper studied the effect of calcium-sulfoaluminate expansive agent on shrinkage and mechanical properties of hardened self-compacting SFRC with a varying volume fraction of steel fiber

Summary

Introduction

To overcome the casting difficulty of concrete in structural members and joints with complex shapes and dense reinforcements, and to reduce the environmental pollution of vibration noise, a high-performance self-compacting steel fiber reinforced concrete (SFRC) becomes more and more applicable in engineering structures [1,2,3,4]. Aslani and Nejadi [8] reported that the drying shrinkage of SCC was reduced by 9.3% at 364 d by directly admixing hooked-end steel fiber (circular section, lf = 60 mm, df = 0.75 mm) with volume fraction vf = 0.38%, but the diameter of J-ring flow was decreased by. Grabois et al [10] studied the self-compacting lightweight concrete which prepared with coarse and fine lightweight aggregates by adding hooked-end steel fiber (circular section, lf = 35 mm, df = 0.55 mm) with volume fraction vf = 0.5%, and the drying shrinkage decreased about 7%, but the V-funnel flow time increased by 30 s

Methods

Results

Conclusion